The above described type of fishing reel is well-known as the double bearing fishing reel.
In such reels, when the fishing line is wound on the spool for fishing, the drag mechanism is used to adjust the transmitting torque of the spool to meet the proof stress of the line. When the spool is subjected to a load overcoming the transmitting torque, a main gear in association with the spool slips with respect to a drive shaft coupled with the handle, thereby preventing the line from being broken due to its undergoing a tension greater than the proof stress.
Generally, there are two methods for fishing. One is to use the drag mechanism to slip the main gear as described above and the other is to handle the fishing rod while playing the hooked fish so as to fish it up in a pulling fashion without using the drag mechanism, even when the line is subjected to a tension which exceeds its proof stress. The latter method is often used by expert anglers.
For the latter method, however, when using a fishing reel provided with a drag mechanism, even when the drag mechanism is adjusted to a maximum drag force, slippage occurs on the friction plate at the drag mechanism when the line is subjected to greater tension by a hooked fish, thereby creating a problem in that the aforesaid fishing method wherein the drag mechanism is not used cannot be adopted.